Like other fork-lift trucks, fork-lift reach trucks comprise a load-carrying portion and a driving portion. The load-carrying portion has a mast which can be composed of several mast sections and which can be extracted to large heights. The feature characteristic of a fork-lift reach truck is that the mast is horizontally movable between a position close to the driving portion and a position remote therefrom. The load-carrying means commonly is a fork where the fork prongs are located within parallel-spaced wheel arms which are mounted on the driving portion and extend away from the driving portion on the two sides of the mast. Such fork-lift reach trucks also have an integrated side shift in many case. The load-carrying means, e.g. the fork, has its back fixed to a slider here which can be moved horizontally on an slider guide. The guide is guided on the mast and can be lifted and lowered by means of the lifting and lowering device. Such a fork-lift reach truck allows to orient the pallet in the rack precisely and quickly with no need for the fork-lift truck to change its position.
It must be sure for a fork-lift reach truck having a side shift that no collision occurs with the wheel arms when the side shift is actuated and the load-carrying means is lowered. The mast with the load-carrying means can be retracted between the wheel arms only when the side shift is in its middle position. It is only in this position of the side shift that the load-carrying means can be lowered between the wheel arms with the lift frame incompletely advanced to the front.
It is known to detect a displacement of the side shift digitally. A hydraulic interlocking is effected which prevents the load-carrying means from being lowered and the mast from being pushed back. The driver initially has to bring the side shift to the middle position before the functions mentioned can be carried out. The disadvantage is that the driver is required to detect the position of the side shift visually and, then, to initiate the sideward shift motion manually to the correct direction via control elements in order to achieve freedom of motion. Besides, the side shift operation has to be completed upon getting at the middle position, for which purpose the driver monitors a relevant display.
DE 100 54 789 A1 has made known an industrial truck in which a side shift is also provided for the load-carrying means. The driving mechanism for the side shift is acted on, depending on operating parameters. This enables it to vary the acceleration and/or speed of the side shift in a nearly infinite way. Such a way avoids elastic deformations and vibrations.
It is the object of the invention to provide a fork-lift reach truck having a side shift the operation of which is simplified and becomes faster.